The present invention relates to a receiver and a transmitter/receiver for digital data including video data and audio data, and more particularly to a receiver and a transmitter/receiver suitable for a recording/reproducing apparatus for recording/reproducing uncompressed video data and compressed video data.
At present, as a transmission method for digital video signals, the SMPTE-259M Standard, namely, the Serial Digital Interface (hereinafter referred to as xe2x80x9cSDIxe2x80x9d) Standard is used generally. As is known, this SDI Standard was established by SMPTE: Society of Motion Picture and Television Engineers, and stipulates methods of converting digital data including video data and audio data into serial data and transmitting the data.
Hereinafter, the digital data transmission method in accordance with the SDI Standard will be described specifically with reference to FIG. 4. In the following description, the transmission method in accordance with the television signal of the NTSC System at 270 Mbps will be described.
FIG. 4 is an explanatory view showing the configuration of one frame in accordance with the SDI Standard. The straight line H in FIG. 4 indicates the horizontal pixels of the television signal, and the numerical values above the straight line H indicate pixel numbers. The straight line V in the same figure indicates the vertical line of the television signal, and the numerical values above the straight line V indicate line numbers.
As shown in FIG. 4, in the SDI Standard, one frame period is divided into a horizontal blanking period, and a vertical blanking period, an optional blanking period and an active video period in each field of a first field and a second field constituting one frame.
The horizontal blanking period is stipulated by the range of the horizontal pixels from pixel number 1440 to 1715. In the horizontal blanking period, its head and end portions are provided with EAV (End of Active Video) and SAV (Start of Active Video), respectively. In the horizontal blanking period between these EAV and SAV, it is possible to transmit ancillary data, such as audio data and user data.
In the active video period, video data for 1440 pixels is multiplexed in every line, and transmitted as serial data at a predetermined clock frequency. One pixel is formed of 8-bit or 10-bit video data.
In the optional blanking period, a period included in the vertical blanking period, video data can be placed and transmitted, just as in the case of the active video period.
By using this SDI Standard, the 4:2:2 component television signal for one channel can be transmitted without using any analog transmission systems, whereby signal deterioration can be prevented.
On the other hand, when video data obtained by digitizing a video signal is processed directly, the data amount of the video data becomes large, thereby requiring a very high data rate (transmission speed). Therefore, when the above-mentioned video data is recorded on a recording medium, such as magnetic tape, for example, sufficient recording time cannot be obtained.
In contrast, a method, wherein video data is compressed by bit rate reduction to the extent that visual deterioration in image quality is not recognized, and then treated, is known as an effective method. More specifically, the DV format established by the High Definition Digital Video Cassette Recorder Committee and described in xe2x80x9cSpecifications of Consumer-Use Digital VCRs using 6.3 mm magnetic tapexe2x80x9d is available as a format obtained by applying the bit rate reduction of a video signal to consumer-use digital VTRs.
In this DV format, data is compressed in two modes depending on the television signal by carrying out bit rate reduction on the basis of DCT (Discrete Cosine Transform).
More specifically, in the DV format, the standard television signal is compressed to 25 Mbps data, and the high definition television signal is compressed to 50 Mbps data. The compressed video data is recorded on magnetic tape together with interleaved audio data, VAUX data used as data attached to the video data, sub-code data and the like. When the data compressed in the 25 Mbps mode is recorded on the magnetic tape, the data for one frame is divided into 10 tracks of the magnetic tape and recorded. In addition, when the data compressed in the 50 Mbps mode is recorded on the magnetic tape, the data for one frame is divided into 20 tracks of the magnetic tape and recorded.
When the video data compressed by bit rate reduction, such as the DV format, is transmitted by using the above-mentioned SDI Standard, it was conventionally necessary to release the compression of the video data once and to return to a base band signal. This is because the SDI Standard stipulates only the transmission method for non-compressed video data, namely, uncompressed video data, instead of compressed video data. Furthermore, the SDI Standard is aimed at video data for one channel, and does not stipulate any transmission methods for transmitting video data for multiple channels.
Therefore, a transmission method capable of multiplexing and transmitting compressed video data by using the SDI Standard without returning the compressed video signal to the base band signal was requested earnestly. To meet this kind of request, the above-mentioned Society of Motion Picture and Television Engineers established the SMPTE-305 Standard, namely, the Serial Data Transport Interface, hereinafter referred to as xe2x80x9cSDTIxe2x80x9d). By using this SDTI Standard, video signals for multiple channels, compressed in accordance with the DV format and MPEG (Moving Picture Experts Group) for example, can be transmitted in accordance with the SDI Standard.
Hereinafter, the digital data transmission method in accordance with the SDTI Standard will be elucidated specifically with reference to FIG. 5. In the following, just as in the case of the SDI Standard shown in FIG. 4, the transmission method in accordance with the television signal of the NTSC System at 270 Mbps will be described.
FIG. 5 is an explanatory view showing a concrete example of the configuration of one frame in accordance with the SDTI Standard.
As shown in FIG. 5, in the SDTI Standard, a one-frame period is provided with EAV, SAV, a horizontal blanking period therebetween, vertical blanking periods and optional blanking periods, just as in the case of the SDI Standard shown in FIG. 4. Furthermore, in the SDTI Standard, areas referred to as payloads corresponding to the active video period in the SDI Standard are provided so that digital data including compressed video data is placed and transmitted. Moreover, the above-mentioned horizontal blanking period in accordance with the SDI Standard is used as a physical layer wherein ancillary data can be placed. However, the type of the ancillary data to be transmitted in accordance with the SDI Standard differs from that in accordance with the SDTI Standard. More specifically, in the SDI Standard, the ancillary data was audio data, user data or the like as described in the above. On the other hand, in the SDTI Standard, audio data is stipulated so as to be placed in the above-mentioned payloads together with compressed video data, and transmitted. Therefore, the SDTI Standard stipulates that data referred to as an SDTI header is generated in every line in accordance with digital data to be placed in the subsequent payload, and placed and transmitted as ancillary data.
Hereinafter, the SDTI header stipulated in the above-mentioned SDTI Standard will be elucidated specifically with reference to FIG. 6. In the following description, data to be transmitted on the basis of the SDI Standard and data to be transmitted on the basis of the SDTI Standard are simply referred to as SDI data and SDTI data, respectively.
FIG. 6 is an explanatory view showing a specific configuration of the SDTI header.
As shown in FIG. 6, in the SDTI header, the data of ADF (Ancillary Data Flag) is placed subsequent to the data of EAV indicating the end of the active video period. The values of ADF and EAV shown in FIG. 6 are stipulated in the SDTI Standard, and are fixed values assigned to the SDI data and the SDTI data in common. In addition, in the SDTI header, the data of DID (Data ID) and the data of SDID (Secondary Data ID) are stored to identify the ancillary data placed in the horizontal blanking period. The values DID=140 and SDID=101 shown in the same figure indicate that the ancillary data is the SDTI header.
Furthermore, the SDTI header is provided with areas, such as Code and Block Type. The code is information used for identifying that the length of the subsequent payload is 1440 words (one word is a word length of 10 bits) or 1920 words for one line, or that the digital data stored in the payload is SDI data. In other words, the SDTI Standard stipulates three fixed values as code values used to identify the above-mentioned 1440 words, 1920 words and SDI data, respectively. The block Type is information used to indicate the length of the block of the compressed video data placed in the payload in block units.
By using the information included in the above-mentioned SDTI header, without checking the digital data in the payload, it is possible to recognize that the digital data is SDTI data.
Returning to FIG. 5, digital data including compressed video data is placed in the payload. When video data compressed in accordance with the DV format is transmitted for example, the video data compressed to 25 Mbps, interleaved audio data, VAUX data, AAUX data and sub-code data are formed into blocks and placed in the payload.
As described in the above, in the SDTI Standard, the SDTI header is added within the horizontal blanking period, and digital data including compressed video data is placed in the payload. For this reason, the SDTI Standard can transmit the above-mentioned digital data including compressed video data by using a transmission path based on the conventional SDI Standard.
A conventional receiver for receiving the above-mentioned SDI data and SDTI data will be elucidated below specifically with reference to FIG. 7.
FIG. 7 is a block diagram showing a configuration of the conventional receiver.
As shown in FIG. 7, the conventional receiver, as an SDI-based processing circuit for receiving and processing SDI data transmitted from an external device, is provided with an input terminal 51, a receiving circuit 52, an SDI decoder 53, a bit rate reduction circuit 54 and a multiplex circuit 56 sequentially connected to the above-mentioned input terminal 51, and an audio processing circuit 55 connected between the SDI decoder 53 and the multiplex circuit 56. The receiving circuit 52 receives the SDI data input to the input terminal 51, carries out serial-parallel conversion processing for the received SDI data, and outputs to the SDI decoder 53. The SDI decoder 53 separates video data and audio data from the SDI data, and outputs to the bit rate reduction circuit 54 and the audio processing circuit 55, respectively. The bit rate reduction circuit 54 carries out compression coding processing for the video data so that the input video data has a predetermined amount of data or less, and outputs to the multiplex circuit 56. The audio processing circuit 55 carries out predetermined data processing including interleave processing for the input audio data, and outputs to the multiplex circuit 56 to record on a subsequent recording medium 63. The multiplex circuit 56 multiplexes the video data from the bit rate reduction circuit 54 and the audio data from the audio processing circuit 55 in a predetermined sequence.
Furthermore, the conventional receiver, as the SDTI-based processing circuit for receiving and processing SDTI data transmitted from an external device, is provided with an input terminal 57, and a receiving circuit 52xe2x80x2, an SDTI decoder 58 and a delay circuit 59 sequentially connected to the above-mentioned input terminal 57. The receiving circuit 52xe2x80x2 receives the SDTI data input to the input terminal 57, carries out serial-parallel conversion processing for the received SDTI data, and outputs to the SDTI decoder 58. The SDTI decoder 58 carries out deformatting processing for the input SDTI data, and outputs to the delay circuit 59. In other words, the SDTI decoder 58 takes out the compressed video data, the interleaved audio data, the VAUX data, the AAUX data and the sub-code data from the data blocks placed in the payloads, and outputs to the delay circuit 59. The delay circuit 59 outputs digital data including the compressed video data from the SDTI decoder 58 with a predetermined time delay.
Furthermore, the conventional receiver is provided with a selection switch 60 connected to the above-mentioned multiplex circuit 56 and the delay circuit 59 and operating on the basis of a control signal from a control circuit 61 in order to output the output data from the SDI-based processing circuit or the SDTI-based processing circuit to the recording medium 63 via a record processing circuit 62. The selection switch 60 carries out selection between the multiplex circuit 56 and the delay circuit 59 on the basis of the control signal input from the control circuit 61, and outputs data output from one of the circuits to the record processing circuit 62. To the selection switch 60, the control circuit 61 outputs the control signal corresponding to a command signal from an external selector not shown. This external selector is included in a known input device for inputting commands from the user. The record processing circuit 62 carries out processing required for recording on the recording medium 63 for the data from the selection switch 60, and records on the recording medium 63.
However, in the above-mentioned conventional receiver, it was necessary to provide two input terminals for inputting the SDI data and the SDTI data, respectively, in order to carry out predetermined data processing for the SDI data and the SDTI data, respectively. For this reason, in the conventional receiver, the number of input terminals was unable to be reduced, and the configuration of the receiver was unable to be simplified. Therefore, in the conventional receiver, it was difficult to reduce its cost.
In the conventional receiver, it was necessary to previously check whether digital data to be transmitted was the SDI data or the SDTI data. In other words, in the conventional receiver, it was necessary to previously check whether the digital data was transmitted in accordance with the transmission format of the SDI Standard or the SDTI Standard. Furthermore, in the SDTI Standard, since uncompressed video data can also be placed in the payloads and transmitted, it was also necessary to previously check whether the video data included in the SDTI data was uncompressed data or compressed data. Therefore, in the conventional receiver, it was necessary to properly connect cables to the corresponding input terminals and processing circuits on the basis of the data transmission format and the presence or absence of compression of the video data checked previously.
The conventional receiver was configured so that the external selector was used to select the SDI-based processing circuit or the SDTI-based processing circuit, and so that the selection switch carried out selection to record data on the recording medium. Therefore, in the conventional receiver, when the selection of the processing circuit was performed incorrectly, the received digital data was unable to be recorded on the recording medium occasionally.
When the conventional receiver was used for a system wherein the SDI data and the SDTI data are mixed, it was necessary to use two cables so that one cable was connected to the input terminal for the SDI data, and so that the other cable was connected to the input terminal for the SDTI data. For this reason, when the conventional receiver was used for the above-mentioned system, the number of cables used in the system increased, and the configuration of the system became complicated. Furthermore, in this system, when the receiver was operated by using only one cable, it was necessary to perform an operation of connecting the cable to the corresponding input terminal in accordance with digital data to be received by the receiver, thereby requiring labor and time for the setup operation of the system.
An object of the present invention is to provide a receiver and a transmitter/receiver capable of receiving compressed (bit rate reduced) video data and uncompressed video data without using plural input terminals, and also capable of automatically distinguishing and carrying out proper data processing.
In order to achieve the above-mentioned object, a receiver in accordance with the present invention comprises:
input means for inputting digital data including uncompressed video data or bit rate reduced video data,
receiving means for receiving the digital data output from the input means,
distinguishing means for distinguishing the digital data output from the receiving means,
first decoding means for taking out the uncompressed video data from the digital data output from the receiving means,
bit rate reduction means for carrying out bit rate reduction processing for the video data from the first decoding means,
second decoding means for taking out the bit rate reduced video data from the digital data output from the receiving means,
selection means for selecting the data from the bit rate reduction means and the data from the second decoding means, and
control means for controlling the selection means on the basis of the result of the distinguishing of the distinguishing means.
According to this configuration, the receiver of the present invention can input the bit rate reduced video data or the uncompressed video data via a common input terminal without using plural input terminals. Furthermore, the receiver can distinguish the video data automatically and can carry out proper data processing.
A receiver in accordance with another aspect of the present invention comprises:
input means for inputting digital data including uncompressed video data or bit rate reduced video data,
receiving means for receiving the digital data output from the input means,
distinguishing means for distinguishing the digital data output from the receiving means,
first decoding means for taking out the uncompressed video data from the digital data output from the receiving means,
bit rate reduction means for carrying out bit rate reduction processing for the video data from the first decoding means,
second decoding means for taking out the bit rate reduced video data from the digital data output from the receiving means,
selection means for outputting the digital data output from the receiving means to the first decoding means or the second decoding means, and
control means for controlling the selection means on the basis of the result of the distinguishing of the distinguishing means.
According to this configuration, the bit rate reduced video data or the uncompressed video data can be input via a common input terminal without using plural input terminals. Furthermore, the video data can be distinguished automatically, and proper data processing can be carried out.
A transmitter/receiver in accordance with the present invention comprises:
input means for inputting digital data including uncompressed video data or bit rate reduced video data,
receiving means for receiving the digital data output from the input means,
distinguishing means for distinguishing the digital data output from the receiving means,
first decoding means for taking out the uncompressed video data from the digital data output from the receiving means,
bit rate reduction means for carrying out bit rate reduction processing for the video data from the first decoding means,
second decoding means for taking out the bit rate reduced video data from the digital data output from the receiving means,
selection means for selecting data from the bit rate reduction means and the data from the second decoding means,
control means for controlling the selection means on the basis of the result of the distinguishing of the distinguishing means, and
transmitting means for transmitting the data from the selection means to an external device.
According to this configuration, the bit rate reduced video data or the uncompressed video data can be input via a common input terminal without using plural input terminals. Furthermore, the video data can be distinguished automatically, and proper data processing can be carried out.
A transmitter/receiver in accordance with another aspect of the present invention comprises:
input means for inputting digital data including uncompressed video data or bit rate reduced video data,
receiving means for receiving the digital data output from the input means,
distinguishing means for distinguishing the digital data output from the receiving means,
first decoding means for taking out the uncompressed video data from the digital data output from the receiving means,
bit rate reduction means for carrying out bit rate reduction processing for the video data from the first decoding means,
second decoding means for taking out the bit rate reduced video data from the digital data output from the receiving means,
selection means for outputting the digital data output from the receiving means to the above-mentioned first decoding means or the second decoding means,
control means for controlling the selection means on the basis of the result of the distinguishing of the distinguishing means, and
transmitting means for transmitting the data from the selection means to an external device.
According to this configuration, the bit rate reduced video data or the uncompressed video data can be input via a common input terminal without using plural input terminals. Furthermore, the video data can be distinguished automatically, and proper data processing can be carried out.
While the novel features of the present invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings.